Emanuele Giaccherini scored the opening goal in the 31st minute, controlling a magnificent long pass from Leonardo Bonucci to slot home.
It was a thoroughly deserved reward for Italy, who more than neutralized the supposedly superior individual skills of Belgium with their organisation and work-rate.
Belgium’s best chance to level was spurned by Romelu Lukaku early in the second half but Italy also had chances to double their lead before Graziano Pelle sealed the win in injury-time.
Torrential rain had pounded Lyon before the match, drenching fans who had mingled peacefully in the city centre, but it eased before kick-off, and the pitch handled the deluge well.
Belgium, roared on by a boisterous support, started brightly as Lukaku almost got behind the Italian defence but this proved to be a rarity in the first half.
Italy adopted a flexible formation which depended on wide players Antonio Candreva and Matteo Darmian flying up and down the flanks in a tactical system which offered a 5-3-2 in defence and a remarkable 3-3-4 when pushing forward.
Belgium seemed unsure how to react as they struggled to find stars Kevin de Bruyne and Eden Hazard out wide and were blocked by the Italian wall through the middle.
The opening goal came in a moment of inspiration from Bonucci, whose raking ball from his own half caught the Belgian defence flat-footed.
Giaccherini killed the pass superbly and calmly curled round Thibaut Courtois from 12 yards to break the deadlock.
It sparked wild celebrations on the Italy bench with coach Antonio Conte suffering a cut lip in the proceedings.
Candreva then had a powerful strike saved but Pelle should have done better than head wide with Courtois out of the picture after Belgium failed to clear a corner.
Belgium displayed more urgency as Italy began to tire late on but cynical fouls from Giorgio Chiellini, Eder and Bonucci all halted potential breaks. The yellow cards were a price worth paying.
Substitute Divock Origi headed over eight minutes from time as Belgimm grew increasingly desperate but it was Italy who came closer to a decisive goal as their own substitute Ciro Immobile had a powerful drive batted away by Courtois.
And the killer blow arrived deep into injury-time when Italy countered and Candreva’s chipped cross was emphatically volleyed home by Pelle.
Group E favourites Belgium are now bottom of the table while Italy sit top after Ireland drew 1-1 with Sweden.
Ireland can take encouragement from the result in their Group E opener overnight, but the result was a cause of great concern for Sweden whose mediocrity contrasted starkly with their opponents’ desire.
Ireland were the better team and Sweden were fortunate to grab an equaliser when Irish defender Ciaran Clark headed a cross into his own goal after Wes Hoolahan had opened the scoring with a splendid strike early in the second half.
It was another misfortune for Ireland at the Stade de France, where they were playing for the first time since Thierry Henry’s infamous handball for France led to a goal that crushed the 2010 World Cup qualifying dreams of the Irish in a playoff.
The match was probably the one the Irish and Swedes had targeted for a win in a section that also features traditional European force Italy and a talented Belgium side.
Martin O’Neill’s Boys in Green, however, can be more optimistic than Erik Hamren’s Blue-Yellows, who did not manage a single shot on target despite the efforts of talisman Zlatan Ibrahimovic, who was kept fairly quiet by Ireland’s defence.
“We have two very, very tough matches coming against two sides that are very classy,” said O’Neill.
“But if I can take anything from the performance today, it was that the players looked accomplished. We have the desire but the players are growing into international football.”
Both teams were backed by hordes of fans and the yellow and green armies brought a festive touch to the Stade de France, in sharp contrast with the violence that has marred the tournament.
O’Neill’s side showed a real desire to win, making two attacking substitutions after Sweden’s equaliser, while the Scandinavians looked slow and toothless until Ireland took a deserved lead three minutes after the break.
Hoolahan struck a superb half-volley into the net from Seamus Coleman’s perfect cross into the area triggering a roar rarely heard in the usually subdued Stade de France.
That acted as a wake-up call for Sweden, who were relying on their enigmatic 34-year-old captain Ibrahimovic.
In the first half, Ibrahimovic looked lost on a pitch where which he won two French Cup and two League Cup trophies and, while he produced the cross that led to Ireland’s own goal, the striker failed to convert a chance in the closing stages.
In the 71st minute, Ibrahimovic made a rare break down the left flank into the area and his cross was headed into his own goal by the unfortunate Clark.
Twelve minutes later, however, Ibrahimovic just failed to connect as Martin Olsson’s cross whizzed in front of him, missing the chance to score an almost certain winner albeit undeserved.
“The feeling right now is disappointment rather than coming back for a draw,” said Hamren.
“For the first 50 minutes Ireland were better. Credit to Ireland. Our attack was really bad in the first half. They were able to close us down.”
In Toulouse, relief ran through Spanish ranks after Gerard Pique’s late header secured a 1-0 victory over the Czech Republic in their opening Group D match.
Coach Vicente del Bosque felt the holders were always in control and bristled a little when it was suggested they should score more.
“Everyone wants to score more but we haven’t been too bad in the last few years with this style,” he said.
“We have the responsibility to win and not just play nicely. Now we’re obviously a bit more optimistic about the future than if we’d drawn.”
The often lugubrious coach repeatedly refused to be drawn into praising individual players, with the exception of one he had left out of the team.
“Iker has been exceptional,” Del Bosque said when asked about how record caps holder Iker Casillas felt about David de Gea playing in goal instead of him.
“It’s not about individuals,” was his response to invitations to praise goalscorer Pique or man-of-the-match Andres Iniesta.
Czech coach Pavel Vrba set a target of four points from the remaining games against Croatia, on Friday, and then Turkey on June 21.
“That should be enough to qualify,” he said.
Although pleased at the way his side defended, he wanted the Czechs to do more in possession and was disappointed not to have achieved more.
“After the first 45 minutes I told my players we had to have more patience when we had the ball. We lost the ball a lot and couldn’t counter-attack without it,” he said.
“But the quality of Spain is at another level to us. Spanish football is the best in Europe, we can see that in their clubs, in the Champions League and Europa League.”
Czech defender Roman Hubnik, who might have scored at both ends early in the second half, promised that his side would play more adventurously from now on.
“We had to defend a lot in a block but we’re going to play more offensively in the other games,” he said.
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